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Believe it or Not, I’m Combinatorically Complete

There are three diatonic major chords in the major scale: I, IV, and V. For today, let’s go with the key of D, so that’s D, G, and A. Sometimes in rock and pop we like to mix up the bass notes a little but keep the major-chord theme, and do a I/V, or a V/I, or whatever. All told there are nine combinations of these three major chords and possible bass notes, including the boring ones (D/D, G/G, A/A). Without the boring ones, you’ve got six: D/G, D/A, G/D, G/A, A/D, and A/A.

Why this lesson in combinatorics? Did this turn into a f’ing math blog?

Hold that thought, we’ll come back to it.

The theme song from “The Greatest American Hero” has pulled into a close second on my favorite-theme-songs list.

Be[D]lieve it or [D/F#]not I'm walki[G]ng on ai[G/B]r
I never t[D]hought I could f[D/F#]eel so free[G] [G/A]
[D]Flying a[D/F#]way on a w[G]ing and a [G#m7b5]prayer

Your ear totally thinks that last line is going to end with G → A or similar, since you’re totally primed for that from the first two lines… but wait! Instead, it’s splendid chromatic bass movement and a splendid m7b5 chord.

(3) Rotation of the 1/4/5 chords over stationary roots, as in the intro:

[A/D] [D] [A/D] [D]
[A/G] [D/G] [A/G] [D/G]
[D/A] [G/A] [A] [A]

If you’re keeping score at home, that’s all possible combinations of 1/4/5 over 1/4/5 other than the boring ones (X/X). Combinatorically complete, and not in a gratuitous “math person writes a jazz song way”!

It also has a key change, which means I should go update my post about TV theme songs with key changes, though I’m not in a huge rush to do that, as I’m basically neutral on this key change. However, apropos to this thread, it suffers from totally-random-stupid-bridge syndrome, which is why it sits just behind Growing Pains on my list of favorite theme songs. Hashtag #bridgesorandom.

(Super-random bridge)
This is too good to be [Fmaj7]true
Look at [Ebmaj7]me, falling for you [G/A] [A] [G/A] [A]
(Back to our comfortable chorus vibe in D)
Be[D]lieve it or [D/F#]not, be[G]lieve it or [G/B]not
Be[D]lieve it or [D/F#]not, be[G]lieve it or [G/B]not
(Unremarkable key change to E)
Be[E]lieve it or [E/G#]not I'm walki[A]ng on ai[A/C#]r...